In the field of wireless data transceiver circuits it is known that prior solutions have used a PIN diode and quarter-wavelength transmission lines as a switch between transmit and receive. Such a prior art solution is known, for example, from U.S. Pat. No. 4,701,724 “Injection Switch and Directional Coupler”. However, these switches consume an large amount of DC power.
It is also known to use GaAs MESFETs to form a single-pole, double-throw switch. However, such GaAs MESFET switches are typically too expensive. It may also be a problem with such GaAs MESFET switches to provide enough power handling capability: a 1W signal has a 20V peak-to-peak swing across 50 ohms, thus requiring the FET switch supply to be at least 20V.
From U.S. Pat. No. 5,606,283 “Monolithic Multi-Function Balanced Switch and Phase Shifter” and U.S. Pat. No. 5,446,464 “Transceiver Module” it is known to use reflective switches. The article by Vidmar, in MICROWAVES & RF, JULY 2000, “Use Transmitting Power FETs for Antenna Switching”, improves on the the design of U.S. Pat. No. 5,446,464 by eliminating the PIN diodes and using the PA devices to provide a reflection to the hybrid coupler and then to the receiver.
However, the approach known in the Vidmar article does not perform the necessary functions in a manner suited to low cost and low power radios. Additionally, extending the known designs mentioned above to allow for a range of functions typically required in a radio transceiver would require additional compromises in cost and performance.
A need therefore exists for a transceiver wherein the abovementioned disadvantage(s) may be alleviated.